Reading Diagnostic Trouble Codes
DIAGNOSTIC CODE INTERPRETATIONThe Engine Control Unit (ECU) monitors operation of the emission control system. Some components are monitored continuously, others only during specified operating conditions. When the ECU detects a malfunction lasting longer than a specified period of time the ECU will generate an error code that can be detected at the diagnostic connector.
There are sixteen diagnostic items (including normal operation) that will generate diagnostic codes. The malfunction codes are erased when the vehicle battery is disconnected for more than ten seconds.
NOTE: If the oxygen sensor is disconnected during engine operation for testing purposes a code will be stored and must be cleared after the test is complete.
To test for oxygen sensor codes drive the vehicle a significant distance and check for diagnostic codes before turning the ignition off. Do not however disconnect the battery with the ignition on or the engine running as permanent damage to the vehicle electronic components may result.
If multiple malfunctions occur the diagnostic codes will be sent sequentially beginning with the lowest number code in ascending order with a 2 second pause between each code.
The Voltmeter needle will deflect for a particular duration and a certain number of times.
FOR EXAMPLE:
Code 13
The needle will deflect one time for approximately 0.5 second. This will represent one unit of ten. There will be approximately a one second delay and then the needle will deflect three times for approximately 0.2 seconds with 0.1 second delay between deflections. This will represent three units of one.
Code 23
The needle will deflect two times for approximately 0.5 second with approximately 0.3 second delay between deflections. This will represent two units of ten. There will be approximately a one second delay and then the needle will deflect three times for approximately 0.2 seconds with 0.1 second delay between deflections. This will represent three units of one.
NOTE:
When battery Voltage is low, no detection of failure is possible. Be sure to check the battery for Voltage and other conditions before starting the test.
Diagnosis item is erased if the battery or the engine control unit connector is disconnected. Do not disconnect the battery before the diagnosis result is completely read.
After check and correction are over, disconnect ground cable for 10 seconds or more from negative terminal of battery and connect it again to make sure that failure code is erased.
Using Voltmeter
1. Connect an analogue Voltmeter to the diagnosis connector.
2. Turn ignition switch to ON, and indication of engine control unit memory contents will immediately start. If the system is in normal condition, pointer of Voltmeter indicates normal pattern. If any abnormality is in memory, the pointer of Voltmeter will deflect, indicating abnormal item as described in "Diagnosis chart". After recording the abnormal item, check and repair each part according to the check items in "Diagnosis Chart".
3. If the defective parts have been repaired, disconnect the negative terminal of battery cable for 10 seconds or more and connect it again to make sure that the abnormal code has been erased.